David Ruchien Liu (traditional Chinese: 劉如謙; pinyin: Liú Rúqiān; born 1973) is an American molecular biologist and organic chemist who is the Thomas Dudley Cabot Professor of the Natural Sciences at Harvard University and the Richard Merkin Professor at the Broad Institute, where he is the director of the Merkin Institute for Transformative Technologies.

As an undergraduate at Harvard, Liu worked with Nobel Prize laureate Elias James Corey and graduated first in his class.

[6] After high school, Liu entered Harvard University, where he excelled academically and graduated in 1994 with a Bachelor of Arts (B.A.)

[7] As an undergraduate, he worked in the synthetic chemistry laboratory of Nobel laureate Elias James Corey and was elected to Phi Beta Kappa.

[7] For being the highest ranking member of Harvard's undergraduate class, the university also awarded Liu its Sophia Freund Prize.

Liu became a Howard Hughes Medical Investigator[13] in 2005 and joined the JASONs, academic science advisors to the U.S. government, in 2009.

[15] In April 2019, Liu delivered a TED talk on base editing in Vancouver at TED2019, resulting in a standing ovation from the live audience.

[21] DNA-Templated Synthesis (DTS) generated some of the first examples of DNA-encoded libraries (DELs), now commonly used in drug discovery efforts in academia and in pharmaceutical companies.

[26] Ensemble Therapeutics was founded in 2004 with funding from Flagship Ventures to develop Liu's work on macrocycles; the company raised about $40M and struck several pharmaceutical partnerships, but was shut down in 2017 before any of its lead compounds had reached the market.